Commit message: Prevent use after free in `DecodePng` kernel.

We are cleaning up the memory in `decode` and then we are using an `OP_REQUIRES` to check an invariant on the `decode` data.

PiperOrigin-RevId: 409299145
Change-Id: I4eb93aaca52483eb202e89b78df07fbb2f6cb254
CVE: CVE-2022-23584
CWE: CWE-416
Vulnerability description: Tensorflow is an Open Source Machine Learning Framework. A malicious user can cause a use after free behavior when decoding PNG images. After `png::CommonFreeDecode(&decode)` gets called, the values of `decode.width` and `decode.height` are in an unspecified state. The fix will be included in TensorFlow 2.8.0. We will also cherrypick this commit on TensorFlow 2.7.1, TensorFlow 2.6.3, and TensorFlow 2.5.3, as these are also affected and still in supported range.

Project: tensorflow
File: decode_image_op.cc

  void DecodePngV2(OpKernelContext* context, StringPiece input) {
    int channel_bits = (data_type_ == DataType::DT_UINT8) ? 8 : 16;
    png::DecodeContext decode;
    OP_REQUIRES(
        context, png::CommonInitDecode(input, channels_, channel_bits, &decode),
        errors::InvalidArgument("Invalid PNG. Failed to initialize decoder."));

    // Verify that width and height are not too large:
    // - verify width and height don't overflow int.
    // - width can later be multiplied by channels_ and sizeof(uint16), so
    //   verify single dimension is not too large.
    // - verify when width and height are multiplied together, there are a few
    //   bits to spare as well.
    const int width = static_cast<int>(decode.width);
    const int height = static_cast<int>(decode.height);
    const int64_t total_size =
        static_cast<int64_t>(width) * static_cast<int64_t>(height);
    if (width != static_cast<int64_t>(decode.width) || width <= 0 ||
        width >= (1LL << 27) || height != static_cast<int64_t>(decode.height) ||
        height <= 0 || height >= (1LL << 27) || total_size >= (1LL << 29)) {
      OP_REQUIRES(context, false,
                  errors::InvalidArgument("PNG size too large for int: ",
                                          decode.width, " by ", decode.height));
    }

    Tensor* output = nullptr;
    Status status;
    // By the existing API, we support decoding PNG with `DecodeGif` op.
    // We need to make sure to return 4-D shapes when using `DecodeGif`.
    if (op_type_ == "DecodeGif") {
      status = context->allocate_output(
          0, TensorShape({1, height, width, decode.channels}), &output);
    } else {
      status = context->allocate_output(
          0, TensorShape({height, width, decode.channels}), &output);
    }

    if (op_type_ == "DecodeBmp") {
      // TODO(b/171060723): Only DecodeBmp as op_type_ is not acceptable here
      // because currently `decode_(jpeg|png|gif)` ops can decode any one of
      // jpeg, png or gif but not bmp. Similarly, `decode_bmp` cannot decode
      // anything but bmp formats. This behavior needs to be revisited. For more
      // details, please refer to the bug.
      OP_REQUIRES(context, false,
                  errors::InvalidArgument(
                      "Trying to decode PNG format using DecodeBmp op. Use "
                      "`decode_png` or `decode_image` instead."));
    } else if (op_type_ == "DecodeAndCropJpeg") {
      OP_REQUIRES(context, false,
                  errors::InvalidArgument(
                      "DecodeAndCropJpeg operation can run on JPEG only, but "
                      "detected PNG."));
    }

    if (!status.ok()) png::CommonFreeDecode(&decode);
    OP_REQUIRES_OK(context, status);

    if (data_type_ == DataType::DT_UINT8) {
      OP_REQUIRES(
          context,
          png::CommonFinishDecode(
              reinterpret_cast<png_bytep>(output->flat<uint8>().data()),
              decode.channels * width * sizeof(uint8), &decode),
          errors::InvalidArgument("Invalid PNG data, size ", input.size()));
    } else if (data_type_ == DataType::DT_UINT16) {
      OP_REQUIRES(
          context,
          png::CommonFinishDecode(
              reinterpret_cast<png_bytep>(output->flat<uint16>().data()),
              decode.channels * width * sizeof(uint16), &decode),
          errors::InvalidArgument("Invalid PNG data, size ", input.size()));
    } else if (data_type_ == DataType::DT_FLOAT) {
      // `png::CommonFinishDecode` does not support `float`. First allocate
      // uint16 buffer for the image and decode in uint16 (lossless). Wrap the
      // buffer in `unique_ptr` so that we don't forget to delete the buffer.
      std::unique_ptr<uint16[]> buffer(
          new uint16[height * width * decode.channels]);
      OP_REQUIRES(
          context,
          png::CommonFinishDecode(reinterpret_cast<png_bytep>(buffer.get()),
                                  decode.channels * width * sizeof(uint16),
                                  &decode),
          errors::InvalidArgument("Invalid PNG data, size ", input.size()));

      // Convert uint16 image data to desired data type.
      // Use eigen threadpooling to speed up the copy operation.
      const auto& device = context->eigen_device<Eigen::ThreadPoolDevice>();
      TTypes<uint16, 3>::UnalignedConstTensor buf(buffer.get(), height, width,
                                                  decode.channels);
      float scale = 1. / std::numeric_limits<uint16>::max();
      // Fill output tensor with desired dtype.
      output->tensor<float, 3>().device(device) = buf.cast<float>() * scale;
    }
  }